Method and apparatus for holding a pair of hollow metal articles together



Nov. 21, 1967 T. E. BUTZ ETAL 3,353,850

\ METHOD AND APPARATUS FOR HOLDING A PAIR OF HOLLOW Y METAL ARTICLESTOGETHER Filed Nov. 9, 1966 Fig. I

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United States Patent 3 353 850 METHOD AND APIARATUS son HOLDING A PAIROF HGLLOW METAL ARTICLES TOGETHER Tom E. Butz, Chagrin Falls, andSeymour N. Schlern,

University Heights, Ohio, assignors to The Farmer Manufacturing Company,a division of Textron Inc, Cleveland, Ohio, a corporation of RhodeIsland Filed Nov. 9, 1966, Ser. No. 593,197 1 Claim. (C1. 285-284)ABSTRACT OF THE DISCLOSURE A joint between a pair of radiator or boilersections which sections each have tapering passages to their interiorswherein a conventionally shaped push nipple with a curved outer surfaceis employed. The nipple is coated with a thin heat resistant plasticcoating. The radiator sections are forced over the coated push nippleand the resulting joint includes areas of metal to metal contact betweenthe push nipple and the radiator passages, as well as areas of plasticforced into the interstices between the outer surface of the push nippleand the passages of the radiator sections. On opposite sides of the areahaving both metal to metal contact and plastic forced into theinterstices there are areas completely bridged over by the plastic whichare essentially free of metal to metal contact.

was-- This is a continuation-in-part of application Ser. No. 442,684,filed Mar. 25, 1965, and now abandoned. This invention relates to amethod and apparatus for holding boiler and radiator sections togetherand for providing a fluid connection therebetween.

Heretofore it has been common practice in the art to manufactureradiators, which comprise a plurality of sections, by making thesections singly and then securing a number of the sections together toprovide a radiator of the desired capacity. Likewise, boilers have beenmade in the same general manner. Since it is necessary that the sectionsalso have means for circulating the steam or other fluid through thesections each section is provided with ports which are in alignment withthose of the other sections, and reversely threaded nipples are threadedinto the ports to provide the fluid connection. The threaded nipples areexpensive both to manufacture and install and had the additionaldisadvantage that the radiator sections could not be placed as closetogether as desired, thus increasing the space and decreasing the heatexchanging capabilities.

It has also been common practice to provide a radiator where the nippleswhich connect the sections called push nipples are not threaded but havea double tapered outer wall which fitted into the tapered wall of theports and radiator or boiler sections and wherein the sections arepushed together under pressure to cause the nipples to seal in thebosses. Such radiators were then held assembled by bolts which extendedfrom one end of the radiator to the other. Such a device is shown inPatent No. 1,384,606. Among the problems encountered in the abovepush-nipple devices is the requirement that very close alignment of thenipple receiving bosses must be maintained, otherwise the nipples wouldcant and provide an imperfect seal. Also, surface imperfections on thenipples and radiator bores as well as out of tolerance surfaces andbores contribute to a certain number of leaking seals with the abovedevices. In addition, through holes in the boiler or radiator sectionsmust be provided for allowing the bolts to extend therethrough, whichnecessitates a coring operation during casting and increases the cost ofmanufacture. The alignment of these holes must also be held to veryclose tolerances. In addition, it requires more time to assemble theradiators, as well as the provision of the through bolts, both of whichare expensive. In an attempt to eliminate the problems of sealing withpush nipples, it has been proposed to provide a lead sleeve over thenipple, as shown in Patent No. 908,985, of Jan. 5, 1909. Although thisprovides some improvement in the seal, lead is of a slippery nature andhas no holding power. Once lead is deformed, it stays deformed.Therefore, it was still necessary to use the through bolts to hold thesections together because of the complete lack of holding power.

The present invention contemplates a method and apparatus whereby anipple of the push type may be used and because of its operation theradiator or boiler sections are secured together without the use of anybolts, clamps or means other than the nipple itself.

Still other advantages of the invention will become more apparent fromthe following description of an embodiment thereof, which is illustratedby the accompanying drawing, and forms a part of this specification.

In the drawings:

FIGURE 1 is a vertical medial sectional View of a nipple used incarrying out this invention on a greatly en- I larged scale with certainfeatures exaggerated to better illustrate its form;

FIGURE 2 is a fragmentary sectional view of a pair of boiler or radiatorsections with the nipple in position joining them together in fluidtight relationship, also with certain features exaggerated for clarity;and,

FIGURE 3 is a somewhat diagrammatic representation of a portion of theinterface between an assembled push nipple and passage wall in aradiator section.

Briefly, this invention contemplates the provision of a push nippleformed of a relatively malleable material, such as malleable iron, whichhas an adhesive coating on the surface thereof, preferably a curedsynthetic resin, which nipple is inserted in the nipple receiving bossesof adjacent radiator or boiler sections and when the sections are forcedtightly over the nipple the nipple will provide a fluid tight connectionbetween the radiator or boiler sections with the nipple providing forfiuid communication between the hollow interiors of the adjacentsections. The push nipple provides the sole structural connectionbetween the radiator or boiler sections without the necessity of usingtie bolts or the like.

More particularly, and referring now to the drawing, and for the presentto FIGURE 1, a medial sectional view of a push nipple for use in thisinvention is shown on a greatly enlarged scale with the outer curvaturethereof exaggerated for clarity of illustration. The push nipple per seis comprised of a tubular malleable iron body member 10 having a throughcentral bore 12 and a curved or tapered outer surface 14. The body 10 isof conventional design configuration. In this design, the outer surface14 from the outer edges 16 inwardly to points 18 is formed with a radiusof curvature R and the surface between the points 18 is formed with aradius of curvatures R R being greater than R It is to be understoodthat the radii R and R used to illustrated these curves are actuallymuch shorter proportionally to the body 10 than are actually present inthe nipple, thus exaggerating these two curves in the drawing toillustrate the outer configuration of the body 10. This combination of alarger radius R than radius R provides for a flatter curve between thepoints 18 at the mid-portion of the nipple and a steeper curvaturetoward the outer edges of the nipple. This configuration also providesfor a greater thickness of the body 10 at its central portion than atits outer edges.

The exterior curved surface 14, as well as the end surfaces 20, of thebody is coated with a layer of adhesive 22. The adhesive is preferablyone of the plastics having the ability to withstand water, steam orother heat exchange liquids. It should have the ability to expand andcontract along with the material of the body and to fill the pores onthe surface of the body as well as the pores of the section to which itis to be engaged. Although shown as covering the outside surfaces only,it is con templated that the entire outside and inside could be coatedwith the adhesive. It is also preferred that the adhesive be of acharacter that the aging of the adhesive be such that it attain acertain degree of hardness. Also, the adhesive should have the abilityto fiow at the time of installation. When the adhesive finallystabilizes, it should be a semi-rigid material. Suitable adhesivesinclude, but are not limited to synthetic resins in the classesincluding polypropylene, urethane, epoxy resins, and the hydrocarbons.

FIGURE 2 shows a pair of radiator or boiler sections 24 in assembledrelationship with an adhesive coated push nipple. Each of the sectionshas a boss 26 which is provided with a tapered frusto conical innersurface 28 having one end 30 communicating with the interior of thesection and an opposite end opening 32. The diameter of the opening 32is greater than the diameter of the body 10 of the push nipple at theends 16 thereof, exclusive of the plastic coating 22. The diameter ofthe opening 30 in the boss is less than the diameter of the body 10 atits central thickest part between points 18. A clearance groove 34 isprovided in each of the bosses 26 adjacent the opening 32, the'clearancegrooves 34 connecting with flat faces 36 on the bosses 26. It should benoted that with respect to FIGURE 2 the actual amount of taper of thebore within the bosses is-exaggerated for clarity of illustration justas the outer curvature of the body It) is also exaggerated in'thisfigure, as well as in FIGURE 1, for the purpose of illustration.

In order to assemble a pair of sections to provide the assembly shown inFIGURE 2, the nipple has one end inserted in one of the bores in onesection and then the other section is brought up to the exposed end ofthe nipple and the bore thereof placed over the nipple. All of thesections may be preassembled in this manner. Then pressure is applied toall of the sections to cause the nipples to be pushed home to theposition shown in FIG- URE 2. Alternatively, two adjacent sections canbe assembled and pushed home and then successive individual sectionsassembled individually and pushed home. It is also contemplated that theassembly may be expedited and that initial stabilization of the adhesivestarted by heating the sections just prior to assembly.

During assembly, the configuration and sizes of the tapered bores andpush nipples are such that a substantial amount of the plastic 22 fromthe surface is displaced .into the clearance spaces 34 and between thefaces 36.

Depending upon the relative sizes and the tolerances of the nipples andthe bores, the clearance spaces 34 may be substantially completelyfilled or only partially filled, as shown in FIGURE 2. Radiator orboiler sections assembled as described herein need no additional tiebolts or other means to maintain them in assembled relationship with thecontrol push nipples providing the total holding power to join thesections together.

Although the reasons for the superior holding power of the assembly.according to the present invention over uncoated push nipple assemblieswith cast iron sections are not completely understood, it is believedthat a combination of metal-to-metal contact and adhesive-to-metalcontact with the adhesive filling the pores and voids or recesses of theadjacent metal surfaces, provides a strong interlocking bond ofsubstantially greater strength than would be obtainable either withconventional metal-tometal contact alone or with a thick adhesivejoining of the parts without forced together metal-to-metal contact.

In order to determine the characteristic of the bond between the pushnipple and the bore of the sections, several radiator sections werejoined together using a push nipple wtih adhesive on the surfacethereof, as described previously, and sections were cut through theradiator at the joints and the cut section polished and examinedmicroscopically at various powers of magnification from 50X to 25 OXThis microscopic examination revealed that the interface between thepush nipple and the surface 28 from the end of the bore 30 to location Ashown in FIG- URE 2 was characterized in that usually the opposite metalsurfaces were definitely spaced from each other with the plasticbridging the space between them with little or no metal-to-metalcontact. The cast iron of the radiator section, to a greater extent, andthe malleable iron of the push nipple, to a lesser extent, both had pitsor pores or void areas which areas were filled with the plastic, thevoids of the cast iron being filled by the plastic being displaced andforced therein during the joining operation. Likewise, the interfacebetween the push-nipple 10 and the surface 28 from the end of the bore32 to the point B, shown in FIGURE 2, were also normally definitelyspaced from each other with similar bridging of the plastic and littleor no metal-to-metal contact. Also, in this section pits and voids inboth the cast iron and malleable iron were filled with the plastic.However, the interface between the points A and B, shown in FIGURE 2,showed regions which appeared to be of essentially metal contact betweenthe outer surface of the body 10 of the push nipple and the surface 28,as well as regions where the metal surfaces were spaced and bridged overwith the plastic. At these bridged-over or filled spaces the opposingmetal surfaces also had areas or voids which the plastic filled. Some ofthe pits and voids which were directly opposite each other had theadhesive extending from inside one pit or void over to and inside theother pit or void. The boundaries of such pits and voids sometimes showsmetal-to-metal contact and in other places a thin layer of adhesivebetween the opposite metal surfaces.

FIGURE 3 is a somewhat diagrammatic representation of a portion of theinterface between points A and B as it appears under magnification ofbetween about 50X and 250 showing areas of essentially metal-to-metalcontact and areas of spaced walls bridged over by the adhesive. It wasalso noted that due to the variations within tolerances of the sizes ofthe tapers in the bosses 26 and the sizes within tolerances with theouter surfaces 14 of the body 10 that the distance between points A andB varied from joint to joint, and even varied on opposite sides of asingle joint. In some cases the distance between points A and B wasrather extensive, whereas in other cases it was a relatively smallportion of the total area forming the joint. Usually, however, thedistance from the surface 30 to point A was somewhat longer or moreextensive than the distance from surface 32 to point B. It was alsonoted that during assembly the outer surface 14 of the body 10 woulddistort and assume generally the configuration of the tapered bore,particularly between the points A and B conforming to any irregularitiesor out of roundness of the bore. As indicated above, it is believed thata combination of this plastic adhesive flowing into the pits and voidsof the adjacent metal surfaces, as well as the metal to-metal contactpresent, coupled with the compressive squeezing action of the radiatorsections on the nipples, provides an extremely strong bond between theradiator sections and the push nipples which resists separation to sucha degree that no additional tie bolts or locking means are needed tomaintain the sections together. It is also believed that the adhesiveflowing between the flat faces 36 of the bosses contribute to some minorextent to the greatly increased bond holding the sections together.

The increased holding power of sections joined by nipples of thisinvention was demonstrated by comparing the strength of sections joinedby adhesive coated nipples according to this invention with sectionsjoined with uncoated similar nipples of the prior art. The tests wereperformed by first joining several sections of radiators with uncoatedpush-nipples according to convention prior art practice, but omittingthe use of tie bolts. The joined sections were then subjected topressure. In all cases the joints failed before the burst pressure ofthe sections was reached and usually this was at a value less than therequired rating of pressure to be withstood. Then similar sections werejoined with push-nipples coated with adhesive according to thisinvention and subjected to pressure. In virtually all cases the requiredpressure rating was exceeded without joint failure and in many cases aradiator section Iburst while the joint continued to hold. These testsdemonstrated the superior holding power of joints formed according tothis invention with adhesive coated push-nipples.

An additional advantage of the plastic coating on the body of thepush-nipple is the increased efiectiveness of the fluid seal between thepush-nipple and the tapered bore even if used in conjunction withconventional tie bolts. The plastic around the nipple and between theinterfaces of the metal provides an extremely good seal, the plasticflowing to all of the exposed areas to prevent fluid leakageto a muchgreater extent than can be achieved with uncoated nipples. In usingprior art uncoated pushnipples for assembling sections, there always wasa certain number of leaking joints caused by imperfections on the matingsurfaces, out of tolerance surfaces, etc.; however, with the adhesivecoated nipples of this invention, virtually no leaking joints have beenencountered.

It is also contemplated that the plastic may be made of a material whichis filled with finely divided metal particles and if the assembly isheated to a suflicient temperature to burn out the filler material, themetal particles remaining will be securely bonded together to provide astrength increasing seal.

Also, filler material can be added to the plastic to strengthen theplastic and/ or raise the temperature which it can attain withoutburning out or being degraded.

It is to be understood that the shape of the outer surface need not belimited to the exact configuration described, it only being necessarythat it taper from a smaller diameter at its ends to a larger diameterat its middle, with the smaller diameter being smaller than the openingof the radiator boss and the larger diameter being larger than thisopening 32 of the boss.

Having thus described the invention in an embodiment thereof, it isrealized that numerous and extensive departures may be made from themethod and apparatus described without departing from the scope of theinvention as defined in the appended claim.

We claim:

Means for joining a pair of hollow cast iron members which members eachhave a passage communicating with the exterior and terminating in anopening and wherein the walls of said passages taper outwardly towardsaid Opening and wherein said passage has a smaller diameter Where itcommunicates with the exterior and a larger diameter at the opposite endthereof, comprising a malleable metal tubular member disposed withineach of said passages to provide interconnection therebetween, saidtubular member having an outer surface which curves from a smallerdiameter at the ends thereof to a larger diameter at the central portionthereof, said tubular member having a portion of its outer diameterlarger than a portion of the diameter of the opening, said outer surfaceof the tubular member having a coating thereon of a synthetic resinhaving the property of adhering to and bonding metals, said resin beingresistant to deterioration at temperatures above 225 F., said outersurface of said malleable member having line contact at tangency witheach of said passages which line contact expands to area contact ondeformation, said expanding area of contact causing a portion of theresin to be forced into interstices between said Walls of the openingand the outer surfaces of said malleable member resulting in said areaof contact having regions of essentially metal to metal contact andregions of resin interposed in the interstices between the metalsurfaces, the opposing surfaces of said malleable member and saidpassages on both sides of said area of contact with each passage wallbeing essentially free of metal to metal contact and bridged by saidresin, whereby a bond-seal is provided by said contact areas and a sealis provided by the bridging resin on each side thereof.

References Cited UNITED STATES PATENTS 2,180,960 11/1939 Kennedy 285284X 2,409,283 10/ 1946 Hudson.

2,643,646 6/1953 Dunn 122-231 3,210,102 10/1965 Joslin 285-284 X3,286,341 11/1966 Miller.

FOREIGN PATENTS 813 1/ 1905 Great Britain. 292,513 8/ 1953 Switzerland.

CARL W. TOMLIN, Primary Examiner. R. G. BERKLEY, Assistant Examiner.

